diff --git a/assets/src/bundles/add_forge/create-request.js b/assets/src/bundles/add_forge/create-request.js
--- a/assets/src/bundles/add_forge/create-request.js
+++ b/assets/src/bundles/add_forge/create-request.js
@@ -23,11 +23,31 @@
         $('#userMessage').removeClass('badge-danger');
         $('#userMessage').addClass('badge-success');
         requestBrowseTable.draw(); // redraw the table to update the list
-      } catch (response) {
-        const responseText = await response.json();
+      } catch (errorResponse) {
         $('#userMessageDetail').empty();
-        $('#userMessage').text('Sorry; an error occurred');
-        $('#userMessageDetail').text(responseText.substring(0, 500));
+
+        let errorMessage;
+        let errorMessageDetail = '';
+        const errorData = await errorResponse.json();
+        // if (errorResponse.content_type === 'text/plain') { // does not work?
+        if (errorResponse.status === 409) {
+          errorMessage = errorData;
+        } else { // assuming json response
+          // const exception = errorData['exception'];
+          errorMessage = 'An error occurred during the request creation';
+          try {
+            const reason = JSON.parse(errorData['reason']);
+            Object.entries(reason).forEach((keys, _) => {
+              const key = keys[0];
+              const message = keys[1][0]; // take only the first issue
+              errorMessageDetail += `\n${key}: ${message}`;
+            });
+          } catch (_) {
+            errorMessageDetail = errorData['reason']; // can't parse it, leave it raw
+          }
+        }
+        $('#userMessage').text(errorMessage);
+        $('#userMessageDetail').text(errorMessageDetail);
         $('#userMessage').removeClass('badge-success');
         $('#userMessage').addClass('badge-danger');
       }
diff --git a/swh/web/settings/development.py b/swh/web/settings/development.py
--- a/swh/web/settings/development.py
+++ b/swh/web/settings/development.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2017-2019  The Software Heritage developers
+# Copyright (C) 2017-2022  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU Affero General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -9,9 +9,16 @@
 
 from django.core.cache import cache
 
+from swh.web.config import get_config
+
 from .common import *  # noqa
 from .common import MIDDLEWARE
 
+swh_web_config = get_config()
+swh_web_config.update(
+    {"features": {"add_forge_now": True,},}
+)
+
 MIDDLEWARE += ["swh.web.common.middlewares.HtmlPrettifyMiddleware"]
 
 AUTH_PASSWORD_VALIDATORS = []  # disable any pwd validation mechanism